From a technical perspective, the 3DXChat offline mod is a feat of reverse engineering that highlights the architecture of modern online games. 3DXChat, like many MMOs, relies heavily on server-side verification. The server dictates the position of avatars, the state of the economy, and the validity of user permissions (such as access to clothing items or room edits).
Since a true mod doesn't exist, players use several "pseudo-offline" methods to achieve the same result: 3dxchat offline mod